Construction and immunogenic evaluation of DNA vaccine expressing influenza A (H1N1) virus hemagglutinin antigen

Abstract

Objective To construct DNA vaccine expressing influenza A ( H1N1) virus hemagglutinin (HA) antigen, and to evaluate its immunogenicity in mice. Methods The condon-optimized influenza A ( H1N1) virus HA sequence was synthesized and transferred to DNA vaccine vector, and its expression efficacy was proved by Western blotting in vitro. BALB/c mice were divided into DNA vaccine group and control group by simple random sampling for the evaluation of DNA vaccine immunogenicity. After the final inoculation, spleens and sera were collected from the immunized mice. HA-specific antibody responses in sera and T cell responses in splenocytes were quantified by ELISA and enzyme-linked immunospot assay ( ELISPOT) , respectively. In addition, hemagglutination inhibition (HI) and neutralizing antibodies were determined by HI assay and pseudovirus based neutralization assay, respectively. The t test was adopted in the comparison between the two groups. Results The constructed DNA vaccine could efficiently express HA protein in vitro. The inoculation of DNA vaccine in mice was capable of inducing vigorous T cell responses [429. 0 ± 113. 4 spot-forming cell (SFC)/106 splenocytes], the binding antibody liters in sera reached 16127.0 ±2698.0, and HI antibody tilers were 100. 8 ± 16. 9. All these data were significantly higher than those in vector control group (t=3.863, P=0.0042; t=5.734, P=0.0002; t =6. 018, P=0.0001, respectively). Furthermore,DNA vaccine could elicit high levels of neutralizing antibodies against homogenous H1N1 virus.but not against H1N1 heterogenous ones.Conclusions The constructed DNA vaccine is highly immunogenic and could induce high level of protective immunity. Key words: Influenza A virus,H1N1 subtype; Vaccines,DNA; Hemagglutinins; Immunogenicity; Neutralization antibody